Plural component spray guns spray two or more components that are mixed together during application. A main component is sprayed from a tip at the center of the nozzle. The base component is shaped into a fan shaped pattern by air flowing from nozzle ports on opposite sides of the main component which are sometimes referred to as "horns". The horns form the main component into a fan shaped pattern to evenly cover a relatively wide area.
In some of these plural component guns, such as the plural component spray gun disclosed and described in U.S. Pat. No. RE 31,163 of Gardner, a catalyzing agent is mixed with atomization air in a mixing chamber before being sprayed from the nozzle. In another spray gun, disclosed and described in U.S. patent application No. 07/557,981, now U.S. Pat. No. 5,303,865, raw catalyst is added to a main component externally by a separate jet near the nozzle without mixing it with air. In the latter plural component spray gun, an injection nozzle injects a catalyst agent into the main component after it is shaped into the fan shaped pattern. It would be advantageous if a catalyst could be added early during the shaping of the fan shaped pattern in order to obtain uniform mixing from top to bottom over the entire width of the fan shaped pattern.
A frequent problem with these plural component guns is clogging of parts after prolonged use and sometimes, early on in use. Components that build up in the passages clog the passages as well as the valves and exit paths. A catalyzing agent, added early at the entrance of assist air for mixing, must pass through the geometry of the gun. As the air atomized catalyst passes through passageways and valves, sharp corners and turns tend to cause the catalyst to "shear out" of the air catalyst stream. Also, according to the boundary layer theory for fluids, there is always a thin layer of static fluid coating the walls of passageways and valves that the mixture passes through. This static fluid has the same or even a larger proportion of atomized catalyst in it as the dynamic fluid and, therefore, catalyst builds up on the walls over a period of time which sometimes is all too short.
The problem with build-up is that the catalysts are typically hazardous to persons and property. When build-up exists inside the gun, it can come out unexpectedly and get on persons or property. This would then require constant attention (maintenance) to insure the gun does not have build-up inside.
It is therefore one object of the present invention to provide a plural component spray gun that reduces chemical build-up in passageways of a plural component spray gun to a minimum.
Another object of the present invention is to provide a plural component spray gun that accomplishes a full mix of catalyzing agent with a base component throughout the entire spray pattern.
Still another object of the present invention is to provide "short path" technology by introducing a catalyzing agent into an air stream as close as possible to the nozzle tip spraying the main component.
Yet another object of the present invention is to introduce a catalyzing agent into the shaping air stream that shapes the main component into a fan shaped pattern.
Still another object of the present invention is to introduce the catalyzing agent into an air stream that shapes the main component at a point near the shaping air exit port.
Yet another object of the present invention is to introduce a catalyzing agent into the shaping air stream through dual injectors on both sides of the main component.
Still another object is to provide a side injector for injecting a catalyst in an air stream without adversely effecting the air flow or disturbing the spray pattern.
Still another object is to provide a side injector for a plural component spray gun that provide a port for catalyst flow verification.
Yet another object of the present invention is to provide a side injector for a plural component spray gun that injects a catalyst after the flow of air and before the main component begins and stops injection before the flow of air stops.